packagegroup-core-security: add missing packages

Changes:
- Add libmhash and libgssglue so they will get tested by CI.
- Switch to MACHINE_ARCH to facilitate the above, but it makes sense
  anyway due to all the machine overrides used in the packagegroup
  definition.  Since this packagegroup is to facilitate testing and
  unlikely to be used by downstreams, it is believed this will have
  minimal impact.

(adapted from 26e745243d)
Signed-off-by: Scott Murray <scott.murray@konsulko.com>

recipes-core/packagegroup/packagegroup-core-security.bb

@@ -3,6 +3,8 @@ LICENSE = "MIT"
 LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302 \
                     file://${COREBASE}/meta/COPYING.MIT;md5=3da9cfbcb788c80a0384361b4de20420"
 
+PACKAGE_ARCH = "${MACHINE_ARCH}"
+
 inherit packagegroup
 
 PACKAGES = "\
@@ -36,6 +38,8 @@ RDEPENDS:packagegroup-security-utils = "\
     fscryptctl \
     glome \
     keyutils \
+    libgssglue \
+    libmhash \
     nmap \
     pinentry \
     softhsm \